Pasture and Hay Crop Nitrogen Fertilization

Richard Taylor, Extension Agronomist;

The very dry spring that we’ve experienced in 2012 has made it questionable as to whether a second or late spring application of nitrogen (N) might be advisable or economical. Thanks to the rainfall last weekend and the possibility of additional rainfall this week and over the coming weekend, another application of N to pastures and hay fields following the first cutting of hay should have a much reduced chance of injuring your grass crop and should also produce additional grazing or second cutting of hay. However to be on the safe side before you apply that additional N fertilizer, take a soil probe, hand trowel or shovel and check the soil moisture level in your soil. What you would like to find is that the subsoil moisture level has recovered and that the crop will be able to not only draw on soil water from the normal 0-8 inches of soil where most of the roots can be found but also can pull water from the deeper soil layers to support growth when temperatures begin to warm up in May and early June.

Hay producers are at the biggest risk for the current moisture to dissipate before the first hay harvest is taken. If you produce hay, you should be certain to check the soil moisture levels before applying N after the first harvest. Even if inadequate soil moisture is present, N fertilizer will promote more top growth and this growth response under unfavorable conditions can lead to plant death or injury reducing stand longevity. Timothy producers should be especially careful since the first harvest often occurs very late in the spring and unless they are using one of the more heat tolerant varieties such as ‘Derby’ stands can be significantly impacted.

Finally, consider using at least some potash (K) fertilizer when fertilizing in the mid-May to mid-June period. I understand that K has become very expensive but it is the best nutrient to add to help forage grasses and legumes to tolerate the heat and drought stresses of summer. In addition if you are growing orchardgrass, there is a growing concern that we are not adequately fertilizing this crop with enough K to balance the N used to promote yields. There is some evidence that the orchardgrass decline problem that we’ve been experiencing in the Mid-Atlantic may, in part, be caused or at least aggravated by too little K fertilizer in relation to the N rate used.

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